Rot-proof fiber product



Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE DANIEL MANSON SIITHERLAND, .13., 0F MORRISVILLE,

No Drawing.

My invention relates to rot-proof fiber products and their resistance, and to m facture of such boar pensive manner.

with special reference to the manufacture of board of that character.

In practice, fiber board is made from fiber pended in a large volume of water. This pulp is brought into a layer of proper thickness, which is partly freed of its water and then dried, either with or without pressure. In making waterproof board according to my preferred process, I

add to it, a waterproofing agent or material, and also a toxic agent or material, which will destroy or render harmless the organisms that deteriorate the fiber,whether termites or the like, or rot-producing organisms in the strict sense.

materials thus incorp used in such quantity or form that when the water of the pulp is removed, a sufiicient amount of waterproofing and toxic materials will remain interspersed amongst the fibers in the board.

terstices amongst the interlaced fibers are charged (though preferably not filled) with the waterproofing material and the toxic material, which last is combined with the waterproofing material mo the fibers are practically covered with these materials and cemented together by them.

As a waterproofing agent may be used any substance or material having this property that can be incorporated with the pulp so as to be properly distributed in the fiber board, such as water-soluble rosin size, rosin-wax size, or wax size. Many materials commonly known as waterproofing agents can be incor- The invention is of special advantage in connection with waterproof board, and I have hereinafter explained 1t BOT-PROOF FIBER PRODUCT Application filed September 10, 1930. Serial 'No. 481,077.

manufacture, such as board made therefrom.

ake possible the manud in a simple and lnexpulp, consisting of wood fiber mixed and suscommercially feasible.

include in the pulp, or

The agents or readily with the pulp,

orated with the pulp are board.

PENNSYLVANIA porated in fiber pulp to water-proof the A great variety of well-known toxic reagents or materials can be used, including the many well-known toxic-metal salts, as well as coal tar creosote, etc. In general, I prefer insoluble toxic salts as the toxic material in the board, and particularly the toxic salts containing copper, zinc, arsenic, or mercury. Such salts (as well as creosote) are, in general, compatiblewith rosin size, and sufliciently powerful and inexpensive to be Being insoluble in water, they readily remain with the fiber when the water of the pulp is drained away; and are not liable to soak or wash out of the board if exposed to the weather, or otherwise wet. On the other hand, they are poisonous to termites attacking the board; and they are dissolved by the cellulosesdecomposing acid secreted by rot-producing organisms, which by means of this acid break down the cellulose to starch, which they can assimilate. The fine particles of such insoluble salts mix and are distributed more or less uniformly and embedded in the waterproofing material in the final fiber A pulp suitable for my purpose may be prepared according to the following for- In other words, the inmula:

Pounds Fiber 1000 Rosin size (bone dry basis) 20 Zinc meta-arsenate, Zn (As 0 3 Water, about 50000 i re or less uniformly, and

The soluble rosin size and the powdered toxic metal salt are thoroughly mixed with a small amount of water, sufiicient to dissolve the rosin size readily, and this mixture is stirred in with the pulp. The pulp is then run ll'lL'O a pressing mold (wet machine with provisions for draining off the water, or otherwise formed into a raw pulp sheet freed of most of the water. This raw sheet "embedded therein, as already mentioned.

In the formula'above given, 50 lbs. of

. creosote may be substituted for the zinc metaarsenate, with equally good toxic effect.-

The creosote has a strong odor which may render the board objectionable for some'purposes, though specially desirable as a lining for moth closets and the like.

Wood has heretofore been rot-proofed by secondary impregnation with various sub stances, and it has been proposed to treat fiber board in the same way. Such impregnation, however, is subject to serious practical drawbacks:

(1) Only. liquids or reagents in solution can be introduced into the pores of. the material in. this way. Water-soluble toxic reagents, however, are easily washed or soaked out of the board.

. (2) To impregnate a board with an insoluble toxic material, a two-step process is necessary; i. e., the board must first be im pregnated with a solution of one reagent, and then with a solution of another reagent which will reactwith the first to precipitate the desired insoluble material in the pores of the'board.

' (3)v The porescan never be completely filled with any solid introduced in solution,- whether bya one-stage or two-stage process,since the solvent water has to be driven out. v i

j (4) It is difl'icult or impossible to effectively rot-proof a thoroughly .waterproofed board by impregnation, since its pores are already filled or clogged with the water proof material. v All of these difiiculties and disadvantages of secondary impregnation are overcome by incor orating .the. rot-proofing and waterproo ng agents or materials in the pulp, as described above: no special operation whatever'is really required, since the pulp is always thoroughly stirred or agitated before formation into a sheet, as a matter of ordinary manufacturing practice.

Having thus described my invention, I claim:

1. A rot and water-proof and termiteproof fiber board, comprising interlaced fibers havin their interstices charged with a waterproo ng material and a toxic agent combined therewith.

2. A rot andwater-proof and termiteproof fiber board, comprising interlaced fibers having their interstices charged with a waterproofing material, and particles of 

